Generally, the display characteristics of monitors (display devices) differ according to each individual product, and in the case of use upon connection to a personal computer, etc., corrections are preferably carried out in accordance with the individual display characteristics. To carry out such corrections, the display characteristics of each individual monitor must be measured and the results must be prepared as objective data in advance. Normally, such data are referred to as the profile data of each individual monitor. In connecting a monitor to a personal computer, by installing the profile data of the monitor in the personal computer, corrections based on the profile data are enabled and universal display results that are not affected by the display characteristics unique to the individual monitor can be obtained.
The representative display characteristics of a color monitor having a function of displaying color images using the three primary colors R, G, and B are the chromaticities of the three primary colors, the white chromaticity, and the tone reproduction characteristics. Here, the white chromaticity is determined as the tone values of the three primary colors R, G, and B that are required to make an individual color monitor perform a white display. When an application program, which is operating on the personal computer, is to make white be displayed on the monitor, the tone values of the three primary colors R, G, and B that have been determined as the white chromaticity are provided to the monitor.
This white chromaticity can be determined by a physical measurement using an optical measuring device, and in many cases with a general, commercial color monitor, the white chromaticity measured in the shipping process is attached as monitor profile data. Also recently, a method of determining the white chromaticity, wherein a special measuring device is not used and a dedicated program is installed in a personal computer, etc., connected to the monitor, has been proposed. For example, Japanese Unexamined Patent Publication No. 2000-029444 discloses a method of measuring the white chromaticity by visual recognition by an operator.
As mentioned above, by preparing monitor profile data indicating the white chromaticity for each individual monitor and performing correction of the white display characteristics based on the profile data, a universal white display that is not affected by the display characteristics unique to each individual monitor can be performed. However, conventional profile data represent the physical white display characteristics of each individual monitor itself and do not indicate the visual perception characteristics as viewed by an operator when the monitor is placed under a specific illumination environment. Thus though for a plurality of color monitors used under the same illumination environment, substantially the same white reproduction characteristics are obtained by correction of the white display characteristics using monitor profile data indicating the white chromaticity measured by a conventional method, the same white reproduction characteristics cannot be obtained for the plurality of color monitors when they are used under different illumination environments. This presents major problems in terms of practical use.
For example, generally in a DTP process for preparing commercial printed matter, several staff members view color monitors to carry out tasks that are divided among them. However, the illumination environments of the rooms in which the respective staff members work will not necessarily be the same. For example, the working environment of an editor inside a publishing firm will normally differ as a matter of course from the working environment of a designer of an external design office. Specifically, each individual illumination environment will differ significantly according to whether the indoor illumination is a fluorescent lamp or a light bulb, the color of the wallpaper in the room, whether or not sunlight shines in, etc. In such cases, even if correction based on the white chromaticity measured by a conventional method (the pure white chromaticity of each monitor) is performed, the white color that each staff member views on the monitor will differ due to being influenced by the corresponding illumination environment. Though measurement of white that takes the illumination into consideration can be made using a measuring device that can make calorimetric measurements in a non-contacting manner (for example, the PR-705 spectroradiometer, made by Photo Research Inc.), such a measuring device is expensive and not suited for general use.
An object of this invention is thus to provide a white chromaticity measuring device for color monitor that enables the white chromaticity, in which the illumination environment of the installation location is considered, to be measured readily.